The present invention relates generally to engine valve actuation.
In U.S. Pat. No. 6,009,841, an engine with a hybrid valvetrain is disclosed in which one intake valve is actuated by a source other than a camshaft. This first intake valve is randomly operable meaning that the valve opening and closing events are independent of engine crankshaft position, thus, a fully variable valve. A second intake valve is actuated by a camshaft and includes a deactivator. Operation of the second valve may be discontinued or restored within one engine cycle, termed selectable intake valve herein. The exhaust valve(s) of the hybrid valvetrain is conventionally camshaft actuated. As disclosed in U.S. Pat. No. 6,009,841, the advantage of such a system over fully camless engine operation is a lower power consumption requirement.
In U.S. Pat. No. 6,009,841, a method is described in which air is admitted using a randomly operable intake valve when the engine is operating in a lowest range in torque, using a selectable intake valve when the engine is operating in a medium range in torque, and using both the randomly operable intake valve and the selectable intake valve when the engine is operating in a highest range in torque. In U.S. Pat. No. 6,009,841, operation based on torque level is taught as a means to limit the electrical energy consumed by the randomly operable valve over the engine operating map.
In U.S. Pat. No. 5,669,341, a method is described in which air is admitted through a smaller randomly operable intake valve when the engine is operating in a lowest range in engine speed, through a larger randomly operable intake valve when the engine is operating in a medium range in engine speed, and through both randomly operable intake valves when the engine is operating in a highest range in engine speed.
In U.S. Pat. No. 5,647,312, a method is described in which air is admitted using a randomly operable intake valve when the engine is operating in a lower range in torque and speed and air is admitted using a selectable intake valve when the engine is operating at higher speed or higher torque. The determination of which valves to actuate is based on predetermined rpm and engine torque levels.
The inventors of the invention disclosed herein have recognized disadvantages with using engine torque or engine speed as the criteria for determining which valves should be operated. U.S. Pat. No. 6,009,841 does not disclose a relationship between engine torque and electrical energy consumption. Thus, the intended reduction in electrical energy consumed may not be realized. Furthermore, the inventors of the present invention recognize that electrical energy consumption is only one energy loss mechanism affected by the valvetrain. The inventors herein have recognized that engine torque and engine speed are arbitrary discriminators for determining which valves should be actuated.
A method for controlling an internal combustion engine having first and second intake valves in which a first parameter related to a first energy loss associated with a first operating mode in which the second valve is deactivated is determined and a second parameter related to a second energy loss associated with a second operating mode in which the first valve is deactivate is determined. One of the first operating mode and the second operating mode is selected based on the first parameter and the second parameter. The second operating mode is selected when the first parameter and the second parameter indicate that the first energy loss is greater than the second energy loss and the first operating mode is selected when the first parameter and the second parameter indicate that the first energy loss is less than the second energy loss.
The inventors of the present invention have recognized that by considering overall energy loss in selecting which valves to actuate, fuel efficiency of the hybrid valvetrain engine is maximized.
Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification.